I have just finished putting together a pair of Half-Changs using a Fostex FE207E unit as the driver. I damped the speakers on all four sides using a cork underlay and on top of that a poly-acoustic batting.

My question is whether or not I have used to much damping. The attached image shows the length it goes down the inside of the cabinet (the red line) - is this too far? I can easily strip out some of the damping so it becomes half as thick (the blue line is the approx original thickness), would this be a good idea? Or is the level of damping ok?

Try listening to them first. If they sound overdamped, remove some of the damping material. Frankly, it's a matter of taste anyway -some people prefer heavily damped sonics, some lightly. I tend to err toward the latter myself, but YMMV. Up side to these boxes is you have a rather large hole for the driver so adding / subracting damping to suit your ears, system, music etc should be a doddle. Remember unless you're of the minimalist persuasion & your room is perfectly symmetrical, you can adjust the damping levels in each box differently, to suit its room position.

The main box should be damped as you would a bass reflex box. The pirpose is primarily to kill any standing waves & high frequency reflections off the inside walls. To this end i usually start with 1/2" or so wool or cotton felt on all the walls.

Of you added the recommended (but not drawn) driver brace, it is an ideal platform to put some damping. From there adding airspace fill will push the box even more aperiodic... if you find the bass is heavy some foam in the slot port (doesn't take much) can push it to completely aperiodic.

As to lining the panels with cork, it is possible that this could be counterproductive, It will lower panel resonance downwards (by adding mass without adding stiffness) so may decrease the boxes ability to dissappear.

Thanks as well planet10. After listening to the finished speakers, I am very, very happy. There doesn't seem to be too many problems with high frequency reflections; higher frequencies can be somewhat overwhelming though, but I'm hoping that some phase plugs (that i think you make planet10?) will smooth the top end out somewhat. Ill put up a larger post with pictures and my building/listening experience in a couple of days. Thanks guys.